The present invention relates to a process for production for ferromanganese having a carbon content of 0.05 to 8% from iron-containing maganese ore by heating a mixture of maganese ore, solid carbon-containing fuel and slag-forming constituents in a rotary kiln to form a reaction product, and subsequently melting ferromanganese from the reaction product which is removed from the rotary kiln and cooled down before the melting.
Ferromanganese is an alloy which contains or consists of 30 to 95% manganese, 0.05 to 8% carbon, up to 1.5% silicon, up to 0.3% phosphorous and the rest iron. Ferromanganese is used principally as a deoxidation agent in steel production, as well as for the production of manganese steels. Ferromanganese is obtained from a mixture of coke, manganese- and iron-ores in a blast furnace or in an electrically heated furnace, particularly in a submerged arc furnace. The manganese-ores containing iron, such as, for example, manganese modules, contain 10 to 50% manganese and up to 30% iron, wherein manganese can be present as MnO.sub.2, Mn.sub.2 O.sub.3, MnO(OH), Mn.sub.3 O.sub.4 as well as MnCO.sub.3, and iron can be present as Fe.sub.2 O.sub.3 as well as (Mn, Fe).sub.2 O.sub.3. It is difficult to even partially separate the gangue before melting the ore, so that a high portion of gangue in the known melt-reduction process must be separated as liquid slag from the produced ferromanganese alloys, which usually is possible only at temperatures more than 1600.degree. C. and therefore causes an undesirably high use of energy.
A process for the production of ferromanganese is known from British Pat. No. 1,316,802 by which a mixture of coal, slag-forming constitutents and manganese, the gangue of which contains SiO.sub.2 and Al.sub.2 O.sub.3, is heated in a cylindrical rotary kiln at temperatures of 1300.degree. C. to form a reaction product, and subsequently the reaction product is removed from the cylindrical rotary kiln and is melted in an electric furnace, whereby ferromanganese is obtained. A considerable disadvantage with this process is that the whole throughput of the cylindrical rotary kiln, including the coal, reaches the melting furnace, and considerable reduction must be accomplished in the melting furnace, because the reduction in the cylindrical rotary kiln is carried out to MnO. In the electric furnace, silicon is used as the reduction agent, which is added as an alloy.
German Auslegeschrift No. 1,014,137 discloses a process for the melting of iron-poor ore in a cylindrical rotary kiln, in which the pulverized ore is mixed with fuel and is heated to temperatures from 1100.degree. to 1300.degree. C., wherein the ore is reduced to metallic iron and magnetic iron oxide compounds, and in which subsequently the magnetic components of the reaction product are separated from the gangue by magnetic separation. Neither British Pat. No. 1,316,802 nor German Auslegeschrift No. 1,104,137 teach how a separation of the gangue can be achieved before melting the ferromanganese without causing work stoppages in the cylindrical rotary kiln and without requiring reduction in the melting furnace.